我已经通过自己的malloc实现并免费使用mmap.现在,由于与free不同,munmap也将length作为参数,因此我将length作为附加信息放在映射的内存中.

我的malloc和free的代码如下所示.我想问一下,如果这段代码是好的还是我仍然遗漏任何东西或以错误的方式做某事.

@H_301_8@void * malloc ( size_t size )
{
    int *plen;
    int len = size + sizeof( size ); // Add sizeof( size ) for holding length.

    plen = mmap( 0,len,PROT_READ | PROT_WRITE,MAP_PRIVATE | MAP_ANONYMOUS,0 );

    *plen = len;                     // First 4 bytes contain length.
    return (void*)(&plen[1]);        // Memory that is after length variable.
}

void free ( void * ptr )
{
    int *plen = (int*)ptr;
    int len;

    plen--;                          // Reach top of memory
    len = *plen;                     // Read length

    munmap( (void*)plen,len );
}